Timing advance mechanism



Dec. 30, 1969 "G. J. LEHNERER 3,486,492

TIMING ADVANCE MECHANISM 1 Filed Nov. '7, 1967 O FUEL SUPPLY LINE l 37 E 39 5 36 4 2 30 32 .44 Y 38- f 1 91/9 -10 FUEL RETURN LINE United States Patent US. Cl. 123139 8 Claims ABSTRACT OF THE DISCLOSURE A pressure compensating device operating in conjunction with a fuel injection pump timing advance mechanism.

This invention relates to a fuel injection pump and more specifically to an automatic timing mechanism having pressure compensating means to control the timing during cranking speeds.

Fuel injection pumps of the type having a fuel pump and distribution means include an annular cam which can be automatically rotated relative to the rotor and pump housing to either advance or retard fuel injection. Means are provided to mechanically shift the cam position relative to its housing to adjust fuel injection timing. The automatic timing control operates in response to engine speed, in other Words advancing injection with an increase in speed. This type of automatic timing mechanism provides adjustment in response to engine speed but does not compensate for sensitivity to pump pressure, and pressure on fuel inlet to the transfer pump. Accordingly, this invention will compensate for these variables. The compensator includes a valve to bypass pressurized fluid around the timing piston at low engine speeds which will permit a retarded position for fuel injection at low engine speeds. The bypass valve is connected in such a manner that it is not affected by small variations in the pressure at the fuel inlet of the transfer pump or by small variations in the transfer pump outlet pressure.

It is an object of this invention to provide a pressure responsive automatic advance timing mechanism for operation with a fuel injection pump.

It is another object of this invention to provide an automatic timing advance mechanism having means to maintain retarded timing of fuel injection at cranking speeds.

It is a further object of this invention to provide a relief valve for bypassing pressurized fluid to permit retarda-' tion of the automatic timing mechanism for a fuel injection pump during cranking and low engine speeds.

The objects of this invention are accomplished by providing an automatic advance timing mechanism in combination with a fuel injection pump. The fuel injection pump is of the type including a rotor assembly defining a distribution portion and a pumping portion. The rotor forms a head in the pumping portion having radially reciprocating plungers operated by cam lobes on the cam in the pump housing. The cam may be advanced or retarded in response to an automatic timing advance mechanism. The timing advance mechanism is pressure responsive and carries a bypass valve bypassing pressurized fluid at relatively low pressure from the transfer pump to permit retardation of the automatic timing mechanism during cranking speeds.

Referring to the drawings, the preferred embodiment of this invention is illustrated in the attached drawings.

FIG. 1 illustrates a cross section view of the fuel injection pump and the automatic timing means.

FIG. 2 is an enlarged cross section view taken on line II-II of FIG. 1.

Referring to the drawings, FIG. 1 illustrates the fuel injection pump and the distribution means of a fuel in- 3,486,492 Patented Dec. 30, 1969 jection system. An automatic timing mechanism is connected to the cam in the fuel injection pump. A rotor 1 is rotatably supported within the pump housing 2 and the distribution sleeve 3. The rotor 1 is driven by the engine (not shown). A governor linkage 4 is connected to the lever 5 which is pivotly supported on the pump housing 2 and connected to the metering valve 6. The lever 5 controls the metering valve 6 for metering the fuel to the injection pump.

The fuel supply line 7 is adapted for connection to a fuel supply which supplies fuel at the fuel supply line pressure. The fuel is supplied to the transfer pump 8 through the passage 9. The transfer pump 8 is rotated by the rotor 1 and is a conventional vane pump for pressurizing fluid in the outlet passage 10. A pressure regulator valve 11 permits bypass of excess pressurized fluid from the pump 8. The pressure in passage 10 will exert a force on the piston 11 compressing the regulating spring 51 until the opening 12 is uncovered. Excess fuel will then be bypassed through the opening 12 and return to the inlet side of the transfer pump 10.

The pressurized fluid in the passage 10 passes through passage 13 to the metering valve 6. The opening of the metering valve 6 is controlled by the governor operating lever 5. The pressurized fluid then passes into the conduit 14 and also through the passage 15. As the rotor 1 is rotated, the radial passages 15 come into registry with the diagonal passages 16 in the rotor 1. As the rotor 1 rotates, the rollers 17 rotate to a position where they are no longer engaging one of the plurality of cam lobes 22. The pressurized fluid passing through the metering valve 6 forces the plungers 19 radially causing the rollers 17 to move radially while pressurized fluid flows into the high pressure chamber 20. Pressurized fluid passes into the high pressure chamber only so long as the radial passages 15 are in registry with the diagonal passages 16 in the rotor 1. When the rotor 1 rotates to a position where the diagonal passage 16 rotates beyond registry with the radial passages 15, the pressurized fluid flowing into the high pressure chamber 20 is terminated. The period during which the radial passages 15 in the distributor sleeve and the diagonal passages 16 in the rotor are in registry and the rate of flow through the metering valve 6 determines the quantity of pressurized fluid received within the high'pressure chamber 20 for each cycle.

The rotor 1 continues to rotate until a roller 17 contacts a rise 21 on the cam lobe 22 at which time the outlet passage 23 is in registry with a delivery passage 24. Delivery passage 24 is in communication with a delivery conduit 25 which is adapted for connection to a cylinder in an engine. As the roller 17 engages the rising portion 21 of the cam lobe 22, the plunger 19 is biased radially which diminishes the volume of the high pressure chamber 20 causing fuel injection through the delivery conduit 25.

The roller continues to rotate until there is no longer registry between the radial delivery passage 24 and the outlet passage 23 in the rotor 1. The angular position of the annular cam 26 determines the timing of fuel injection. The angular position of the cam 26 can be adjusted manually and is automatically controlled by movement of the control arm 27. The control arm 27 has a spherical end received within a transverse slot 28 of the spring biased timing piston 29. The timing piston 29 is biased to a left-hand position as shown in its normally retarded position. A spring 30 is received within the spring chamber 31 which is vented through the vent 32 to the atmosphere. The vent can be either external or internal.

The timing cylinder 33 receives the piston 29 which reciprocates within the cylinder. The chamber 34 receives pressurized fluid from the transfer pump '8 through the conduit 14 which may be internal or external. As the pressure of the pressurized fluid in the chamber 34 increases the piston 29 is biased to move in the right hand direction to overcome the force of spring 30. At low engine speeds and corresponding low pressures, pressurized fluid in chamber 34 passes through the bypass passages 35 and 36 which are connected on opposing sides of the bypass valve 37 and seal 52. The bypass valve consists essentially of a spring biased plunger 38 retained in position by a snap ring 39. The pressurized fluid in chamber 34 passes through passages 35 and 36 and the chamber 40 and returns through the conduit 41, which may be internal or external, to the fuel return line and the low pressure side of the transfer pump 8.

The pressure developed by the transfer pump 8 is proportional generally to the speed of the engine. At low engine speeds the pressurized fluid in chamber 34 is not suflicient to bias the piston 29 to move in a right-hand direction and the fluid is bypassed through the piston 29 and returned to the fuel return line. The pressure differential across the transfer pump determines the position of the timing piston relative to a timing cylinder 33. During cranking and low speeds, the pressure in chamber 34 is insuflicient to operate the timing piston which thereby permits a retarded position of the cam member 26 during cranking and low engine speeds.

The quantity of charge transferred to the high pressure chamber 20 is determined by the engine speed and load. The supply line 7 supplies fuel at the low side of the transfer pump 8. The transfer pump 8 pumps fuel causing the pressurization for supplying fuel through the metering valve 6 to the high pressure chamber 20. The transfer pump is provided with a pressure regulator valve 11 to maintain the predetermined pressure on the fuel supplied to the metering valve 6. The metering valve 6 is essentially a governor controlled valve which meters the fuel at a rate responsive to engine speed. As the fuel from the output side of the transfer pump 8 passes through the passage 13, it is metered by the valve 6 and supplied to the chamber 20 only when the rotor 1 rotates to a position when the radial passage 15 is in registry with the oblique passages 16 in the rotor 1. The registry of these passages for a limited period of time and the rate of fuel flow through the metering valve 6 determines the charge in the chamber for each cycle. The plungers 19 in the transverse bore 43 are biased radially outward in response to the amount of fuel supplied to the chamber 20 when the passages 15 and 16 are in registry.

Subsequent to the charging of chamber 20, the rotor 1 continues to rotate until the rollers -17 engage the rising portion 21 of the cam lobe 22. Continued rotation of the rotor will cause the plungers to move radially inward against the fluid in the high pressure chamber 20 causing the pressurized fluid to flow through the outlet passage 23. The radial delivery passage 24 is in communication with outlet passage 23 to permit the flow of pressurized fluid from the delivery conduit 25. The pressurized fluid is delivered through the conduit 25 to a combustion chamber of a disel engine. Injection to the combustion chamber during compression causes the firing of the combustible material in the internal combustion engine, which drives the engine.

The timing mechanism operates in the following manner: Initially, the position of the cam 26 is set for timing of injection into the combustion chamber. An advance of injection is sometimes advantageous when the engine is rotating at a faster speed. This is controlled by angularly positioning the annular cam 26. This is accomplished by forcing the arm 27 to rotate against rotation of the rotor 1.

When the engine is stationary, the piston 29 is biased to the left-hand position as shown in FIG. 1 in response to the biasing force of spring 30. As the engine is being cranked, the transfer pump 8 is operating at a low speed with low pressure output. The low pressure fluid transmitted through conduit 14 to the chamber 34 in timing cylinder 33 permits the timing piston 28 .to remain in the left-hand position. The pressurized fluid passes through the passages 35 and 36 and chamber 40 in piston 29. The bypass condition of pressurized fluid exists when the engine is operating at cranking and low speeds.

The pressurized fluid delivered from the transfer pump 8 through the metering velve 6 continues to bypass the timing piston 29 until sufficient engine speed is gained. At a predetermined speed the pressurized fluid biases the plunger 38 to cut off passage 35 which in turn unseats the timing piston 29 from the left-hand position on the stop 44. The piston then moves in the right-hand direction causing the cam 26 to rotate which in turn advances injection timing of the engine. The rate of advance of injection from the time that the piston 38 is biased and the port 35 is sealed off is then in response to the balance of the pressure on the delivery side of the transfer pump 8 upstream of the metering valve, which is essentially a function of engine speed, and the force exerted on the piston 28 by the spring 30.

Any pressure fluctuation on the input side of the transfer pump is compensated for because of the differential pressure across the transfer pump providing the means for controlling movement of the timing piston 29. Accordingly, it can be seen that this device will provide compensation to permit a retarded position of the timing mechanism at cranking and low engine speeds. At engine speeds above cranking speeds the bypass valve is closed and the timing is controlled as a function essentially of engine speed.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A timing mechanism for operation on a fuel injection pump having fuel distribution means adapted for connection to an injection nozzle means on an internal combustion engine, said injection pump including a rotor driving a transfer pump at a rate responsive to engine speed adapted for connection to a fuel supply line and for supplying fuel to said injection pump, a timing cam in said fuel injection pump angularly adjustable relative to said rotor, wherein the improvement comprises a retarding means including, an automatic timing mechanism connected to said cam including a timing piston operating in a timing cylinder hydraulically connected across said transfer pump to operate in response to differential pressure across said transfer pump, a bypass valve means connected across said timing piston operating in response to a predetermined pressure differential across said transfer pump, said bypass valve remaining open for low pressure differential and permitting retardation of said timing mechanism when said engine is operating at cranking and low engine speed.

2. A timing mechanism on a fuel injection pump as set forth in claim 1 wherein a spring biased plunger in said bypass valve means is biased to an open position to permit retardation of the timing mechanism when said engine is operating at cranking and low engine speeds.

3. A timing mechanism on a fuel injection pump having retarding means as set forth in claim 1 wherein restricted passage means communicate with said bypass valve means between the high pressure and low pressure side of said timing piston to restrict the flow of fluid through said valve means.

4. A timing mechanism on a fuel injection pump as set forth in claim 1 wherein said retarding means includes a bypass valve means including a spring loaded plunger biased to an open position permitting the flow of pressurized fluid through said valve means and to return through the fuel line for low pressure differentials across said transfer pump and said piston is spring biased to a return position to thereby permit said timing mechanism to return to a retarded position.

5. A timing mechanism for use on a fuel injection pump as set forth in claim 1 wherein said timing piston includes a bypass valve means including a spring loaded plunger carried in a spring biased piston both of which are biased to an extreme position against the force of pressurized fluid on the high pressure side of said transfer pump and bypassing pressurized fluid through said timing piston permitting said timing mechanism to return to its retarded position when said engine is operating at cranking and low engine speeds.

6. A timing mechanism on a fuel injection pump as set forth in claim 1 wherein said transfer pump is a vane pump and operates in response to engine speed to thereby supply pressurized fluid to said timing piston with a pressure increasing in proportion to engine speed, and said bypass valve means bypasses pressurized fluid across said timing piston to permit retardation of the timing mechanism during low engine speed and cranking speed.

7. A timing mechanism on a fuel injection pump as set forth in claim 1 wherein said timing piston includes a concentric bypass valve means permitting the flow of pressurized fluid through said piston for retarding of fuel injection when said engine is operating at cranking speed.

8. A timing mechanism for a fuel injection pump as set forth in claim 1 wherein said timing mechanism includes a valve means defining a bypass port leading through a plunger chamber to permit flow of pressurized fluid through said plunger chamber when said plunger uncovers said port during low engine speed for retardation of the timing mechanism.

References Cited UNITED STATES PATENTS 3,051,154 8/1962 Kemp.

LAURENCE M. GOODRIDGE, Primary Examiner US. Cl. X.R. 103-2 

